Incorporating a Ferrous Polymer Target into Elastomeric Liners for Socket Fit Sensing in Prosthesis Users.

Area of Science:

• Biomedical Engineering
• Materials Science
• Prosthetics and Orthotics

Background:

• Continuous monitoring of liner-to-socket distance is crucial for maintaining prosthetic fit in trans-tibial amputees.
• A key challenge is integrating thin, uniform target materials into diverse prosthetic liners.
• Existing methods lack practicality for widespread clinical application.

Purpose of the Study:

• To develop and evaluate a novel method for fabricating prosthetic liners suitable for inductive sensing.
• To assess the feasibility of using these liners for continuous socket fit monitoring.
• To determine the accuracy and stability of the sensor over time.

Main Methods:

• A composite material comprising a ferrous polymer (SEEPS polymer and iron powder) and a non-ferrous SEEPS polymer layer was fabricated.
• This construct was integrated into an off-the-shelf prosthetic liner, replacing the original backing.
• Bench testing and in-vivo wear testing (28 days) were conducted to evaluate fabrication accuracy and sensor performance.

Main Results:

• The fabrication process achieved a root-mean-square error of 58 μm in thickness, ensuring consistent calibration.
• During wear, an initial distance offset was observed, which stabilized after approximately 12 days.
• After correction for this offset, the sensor maintained calibration within 4.4% for the clinically relevant distance range (0.00-5.00 mm).

Conclusions:

• The developed ferrous prosthetic liners are a viable method for continuous socket fit monitoring using inductive sensing.
• Pre-wearing of the liners is recommended to establish a stable distance reference before clinical use.
• This technology holds promise for improving prosthetic management and user comfort.